Stonehenge is one of the UK's most popular tourist attractions, drawing 1.5m visitors alone last year. But plans to build a road tunnel nearby to help ease congestion have enraged some archaeologists.

Here is the background to the row.

Why is a tunnel being built?

Image copyrightPA

Visitors to Stonehenge typically arrive there via the A303, a major link road between London and the South West.

However, the single carriageway section of road past the site is a notorious bottleneck, especially in the summer months.

Traffic is typically at twice the level the road was designed to accommodate, says Highways England.

It also runs just 165m (180yds) away from the stone circle.

Plans to upgrade the section of road to a dual carriageway were adopted by the government in 2014. However, a 1.9-mile (3km) tunnel would be dug nearby to hide the traffic as it goes past Stonehenge.

Why are people against it?

Image copyrightUniversity of BuckinghamImage caption
Wild cattle footprints dating back 6,000 years have been found at Blick Mead

Opponents fear building the tunnel could result in the destruction of undiscovered archaeological evidence which could help shed more light on the history of the site and, in particular, why the stone circle was erected.

"There would be extensive tunnel cuttings into the chalk for four lanes of tarmac, and massive highway interchanges through sensitive archaeological areas."

It says the outstanding universal value of Stonehenge transcends any consideration of sorting out a 21st Century part-time traffic jam. It has set up a petition to stop the tunnel being built.

"Traffic will decrease over coming years and it seems very wrong to be spending that amount of money on something that will cause irreparable damage to the World Heritage Site," said Kate Fielden, the alliance's honorary secretary.

"There are so many things that are uncertain. There's what will happen to the water table and how a change in the moisture of the earth could affect how artefacts are preserved.

"Then there's the geology - soft chalk is not the best material to be tunnelling through. Can we assure it's water tight? There's so much we don't know."

The International Council on Monuments and Sites (Icomos), which advises Unesco, said the plans were "severely flawed" and the "whole project must be re-assessed".

What's the latest row about?

Highways England workers monitoring water levels recently dug a 3.5m deep hole at Blick Mead, about 1.5 miles (2.4km) from Stonehenge. However, archaeologists claim they have disturbed a newly-discovered man-made platform dating back 6,000 years.